1. The Field of the Invention
The invention relates generally to alignment of components and subcomponents of an optical assembly.
2. The Relevant Technology
Problems are often encountered when positioning components and sub-components of optical assemblies. One type of optical assembly is an optical package. Optical packages and other optical assemblies can include components such as an active optical device attached to a leadframe. Die attach can provide the mechanical support between the active optical device and the leadframe. Die attach (also known as die mount or die bond) is the process of attaching a silicon component to the die pad or die cavity of the support structure (e.g., the leadframe) of the semiconductor package. There are two common die attach processes, i.e. adhesive die attach and eutectic die attach. Both of these processes use special die attach equipment and die attach tools to mount the die.
A mold compound can protect the optical device mechanically and environmentally from the outside environment. Transfer molding, injection molding, or other molding processes can be used to at least partially encapsulate many packages and are often used to encapsulate leadframe based packages. The leadframe can include, or be coupled to, conductors (e.g. lead fingers for a leadframe) or conductive traces as well as terminal contacts (e.g. metal leads or solder balls) for making electrical connection from outside of the package.
Placement machines can be programmed with component positional information derived from CAD data generated during the design and manufacture of the assembly. The edges of a leadframe are typically referenced for positioning components of an assembly on a leadframe. However, leadframes can change shape from part to part, and even the most accurate and precise mechanical referencing can still result in positional variation between the programmed position of a component and its actual position on a leadframe.
In addition, different components requiring accurate placement and/or optical alignment can be located on different parts of the optical package, which can be later assembled into the optical package or optical assemblies thereby compounding overall tolerances for alignment. For example, an active optical device (e.g. a laser, light emitting diode or a photodiode receiver) located upon a substrate or a leadframe may need to be aligned with an additional component (e.g. a lens, barrel, or interface) located on other pieces of the device (e.g. a lid piece).
An active optical device and a leadframe may be manufactured separate from a lid and a lens. However, alignment of the active optical device with the lens can be difficult where there are several stackable tolerances between the various processes required to manufacture the final optical device. For example, there can be molding processes, attaching processes, cutting processes, drilling processes, and etching processes that contribute to an overall tolerance for aligning an active optical device with a lens. In addition, where the different components, such as the active optical device and the lens, are located on different parts of the device that must be later assembled, such as the base and the lid, the assembly or attachment of the base with the lid must also be held within the stackable tolerances. Thus, what would be advantageous are methods and apparatuses for accurate placement of components of an optical assembly.